The Church offers us different prayers that we can say every day of the week for the faithful departed. These are especially useful for offering a novena on behalf of the dead, or for praying during those seasons of the year (November, in the Western Church; Lent, in the Eastern Church) designated by the Church as times of fervent prayer for the dead.
This prayer is said on Mondays for the souls of the faithful departed.
Monday Prayer for the Faithful Departed
O Lord God omnipotent, I beseech Thee by the Precious Blood which Thy divine Son Jesus shed in His cruel scourging, deliver the souls in purgatory, and among them all, especially that soul which is nearest to its entrance into Thy glory, that it may soon begin to praise and bless Thee for ever. Amen.